KR102544403B1 - Delayed Fluorescence compound, and Organic light emitting diode device and Display device using the same - Google Patents

Abstract

In the present invention, the electron donor moiety of acridine is directly or through a substituted or unsubstituted benzene linker, substituted or unsubstituted triazine, substituted or unsubstituted dibenzothiophene An electron acceptor selected from sulfone (dibenzothiophene), substituted or unsubstituted diphenylsulfone, substituted or unsubstituted 4-azabenzimidazole, and substituted or unsubstituted benzimidazole. A delayed fluorescent compound having a molecular formula of a structure bound to a moiety is provided.

Description

Delayed Fluorescence compound, and Organic light emitting diode device and Display device using the same}

The present invention relates to a luminescent material. More specifically, it relates to a delayed fluorescent compound having improved light emitting efficiency by intramolecular charge transfer, an organic light emitting diode device and a display device including the same.

Recently, demand for a flat display device that occupies less space is increasing according to the size of the display device. is developing into

An organic light emitting diode device emits light when electrons and holes are injected from the cathode and anode into the light emitting material layer formed between the electron injecting electrode (cathode) and the hole injecting electrode (anode), and then the electrons and holes form pairs and then disappear. . The device can be formed on a flexible transparent substrate such as plastic, can be driven at a low voltage (less than 10V), consumes relatively little power, and has excellent color sense.

An organic light emitting diode device is formed on a substrate and includes a first electrode serving as an anode, a second electrode spaced apart from and facing the first electrode, and an organic light emitting layer positioned between the first electrode and the second electrode.

In order to improve luminous efficiency, the organic light emitting layer includes a hole injection layer (HIL), a hole transporting layer (HTL), and an emitting material layer (EML) sequentially stacked on the first electrode. , an electron transporting layer (ETL), and an electron injection layer (EIL).

Holes move from the first electrode, which is an anode, to the light emitting material layer through the hole injection layer and the hole transport layer, and electrons move from the second electrode, which is a cathode, to the light emitting material layer through the electron injection layer and the electron transport layer.

Holes and electrons moved to the light-emitting material layer combine to form excitons, and are excited to an unstable energy state, then return to a stable energy state to emit light.

The external quantum efficiency (η _ext ) of the light emitting material used in the light emitting material layer can be obtained by the following formula.

η _ext = η _int × г × Φ × η _{out - coupling}

(Where, η _int : internal quantum efficiency, г: charge balance factor, Φ: radiative quantum efficiency, η _{out - coupling} : out coupling efficiency)

Charge balance factor (г) means the balance of electrons and holes that form exciton, and generally has a value of '1' assuming 1:1 matching of 100%. Radiative quantum efficiency (Φ) is a value related to the luminous efficiency of the actual light emitting material, and in the host-dopant system, it depends on the fluorescence quantum efficiency of the dopant.

The internal quantum efficiency (η _int ) is the rate at which generated excitons are converted into light, and has a limiting value of up to 0.25 in the case of fluorescent materials. When an exciton is formed by combining a hole and an electron, a singlet exciton and a triplet exciton are generated at a ratio of 1:3 according to the spin arrangement. However, in fluorescent materials, only singlet excitons participate in light emission, and the remaining 75% of triplet excitons do not participate in light emission.

Out coupling efficiency (η _{out - coupling} ) is the ratio of light extracted to the outside among emitted light. In general, when isotropic molecules are thermally deposited to form a thin film, individual light emitting molecules do not have a certain directionality and exist in a disordered state. The out-coupling efficiency in this random orientation state is generally assumed to be 0.2.

Therefore, the maximum light emitting efficiency of the organic light emitting diode device using the fluorescent material is about 5% or less.

In order to overcome the low efficiency problem of fluorescent materials, a phosphorescent material having a light emitting mechanism that converts both singlet excitons and triplet excitons into light has been developed.

In the case of red and green, phosphorescent materials having high luminous efficiency have been developed, but in the case of blue, phosphorescent materials satisfying the required luminous efficiency and reliability have not been developed.

Therefore, in a fluorescent material that satisfies reliability, there is a need to develop a material capable of increasing luminous efficiency by increasing quantum efficiency.

The present invention is intended to solve the problem of low quantum efficiency of fluorescent materials.

In order to solve the above problems, the present invention provides a molecular delayed fluorescent compound in which an electron acceptor moiety is bonded directly or through a linker to an acridine electron donor moiety.

The electron accepting moiety is a substituted or unsubstituted triazine, a substituted or unsubstituted dibenzothiophenesulfone, a substituted or unsubstituted diphenylsulfone, a substituted or unsubstituted 4-azabenzimidazole, a substituted or unsubstituted dibenzothiophenesulfone, or a substituted or unsubstituted diphenylsulfone. benzimidazoles.

That is, the delayed fluorescent compound of the present invention is represented by the following chemical formula, n is 0 or 1, X is a substituted or unsubstituted triazine, a substituted or unsubstituted dibenzothiophenesulfone, or a substituted or unsubstituted dibenzothiophenesulfone. phenylsulfone, substituted or unsubstituted 4-azabenzimidazole, substituted or unsubstituted benzimidazole, and Y is substituted or unsubstituted benzene.

In addition, the present invention provides an organic light emitting diode device and a display device in which the organic light emitting layer includes the above delayed fluorescent compound.

The delayed fluorescent compound of the present invention has a structure in which an electron donor moiety is bonded to an electron acceptor moiety by a linker, so that charge transfer easily occurs in the molecule and luminous efficiency is improved. In particular, since excitons in a triplet state are used for light emission in the delayed fluorescent compound of the present invention, the light emission efficiency of the delayed fluorescent compound is improved.

In addition, since acridine having a hexagonal structure is used as the electron donor moiety, steric hindrance with the electron acceptor moiety increases and the dihedral angle between the acridine electron donor moiety and the electron acceptor moiety increases. Therefore, since the formation of conjugation between the electron donor moiety and the electron acceptor moiety is restricted and the separation between the HOMO and the LUMO occurs smoothly, the improvement in luminous efficiency is further increased.

In addition, a dipole is formed from the electron-donor moiety to the electron-acceptor moiety to increase the dipole moment inside the molecule, thereby further increasing the luminous efficiency.

In addition, the electron donor moiety and the electron acceptor moiety are combined in the molecule, and the overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is reduced. A field activated delayed fluorescence complex is formed, and the luminous efficiency of the delayed fluorescence compound is further improved.

As the distance between the electron-donor moiety and the electron-acceptor moiety increases by the linker, the overlap between the HOMO and the LUMO decreases, thereby reducing the difference between triplet energy and singlet energy (ΔE _ST ).

In addition, it is possible to minimize the red shift problem of light emitted from the light emitting layer including the delayed fluorescent compound due to the steric hindrance of the linker.

Therefore, the organic light emitting diode device and the display device including the delayed fluorescent compound of the present invention can improve luminous efficiency and implement high quality images.

1 is a view for explaining a light emission mechanism of a delayed fluorescent compound according to an embodiment of the present invention.
2a and 2b are diagrams for explaining the molecular structure of a compound containing a carbazole electron-donating moiety.
3A and 3B are diagrams for explaining the molecular structure of a compound containing an acridine electron-donating moiety.
4a to 4d are graphs showing delayed fluorescence characteristics of delayed fluorescence compounds according to embodiments of the present invention.
5 is a schematic cross-sectional view of an organic light emitting diode device according to an embodiment of the present invention.

In the present invention, an electron-donating moiety of acridine is directly substituted or unsubstituted through a benzene linker, substituted or unsubstituted triazine, substituted or unsubstituted dibenzothiophenesulfone (dibenzothiophene), substituted or unsubstituted diphenylsulfone, substituted or unsubstituted 4-azabenzimidazole, and substituted or unsubstituted benzimidazole. A delayed fluorescent compound having a molecular formula of a structure bonded to t is provided.

In another aspect, the present invention provides a delayed fluorescent compound represented by the following formula 1, X is selected from the following formula 2, and Y is selected from the following formula 3. (n is 0 or 1)

[Formula 1]

[Formula 2]

[Formula 3]

(In Formula 2, each of R1 to R4 is independently selected from substituted or unsubstituted aryl, and in Formula 3, each of R5 and R6 is independently selected from hydrogen or C1-C10 alkyl.)

The delayed fluorescent substance of the present invention may be any one of the following compounds.

In the delayed fluorescent substance of the present invention, a difference between singlet energy and triplet energy of the delayed fluorescent compound may be 0.3 eV or less.

From another point of view, the present invention includes a first electrode, a second electrode facing the first electrode, and an organic light emitting layer positioned between the first and second electrodes, wherein the organic light emitting layer comprises acridine (acridine) electron-donating moiety is directly or through a substituted or unsubstituted benzene linker Substituted or unsubstituted triazine (triazine), substituted or unsubstituted dibenzothiophene (dibenzothiophene), substituted or unsubstituted Molecular formula of a structure bound to an electron acceptor moiety selected from unsubstituted diphenylsulfone, substituted or unsubstituted 4-azabenzimidazole, and substituted or unsubstituted benzimidazole It provides an organic light emitting diode device comprising a delayed fluorescence compound having a.

From another point of view, the present invention includes a first electrode, a second electrode facing the first electrode, and an organic light emitting layer positioned between the first and second electrodes, wherein the organic light emitting layer comprises Chemical Formula 1 below. , wherein X is selected from Formula 2 below, and Y is selected from Formula 3 below. (n is 0 or 1)

[Formula 1]

[Formula 2]

[Formula 3]

(In Formula 2, each of R1 to R4 is independently selected from substituted or unsubstituted aryl, and in Formula 3, each of R5 and R6 is independently selected from hydrogen or C1-C10 alkyl.)

In the organic light emitting diode device of the present invention, the delayed fluorescent compound may be any one of the following compounds.

In the organic light emitting diode device of the present invention, a difference between singlet energy and triplet energy of the delayed fluorescent compound may be 0.3 eV or less.

In the organic light emitting diode device of the present invention, the delayed fluorescent compound is used as a dopant, and the organic light emitting layer may further include a host.

In the organic light emitting diode device of the present invention, the difference between the highest level occupied molecular orbital level of the host (HOMO _Host ) and the highest level occupied molecular orbital level of the dopant (HOMO _Dopant ) (|HOMO _Host -HOMO _Dopant |) or the host The difference (|LUMO Host -LUMO _{Dopant |} ) between the lowest level unoccupied molecular orbital level (LUMO _Host ) of the dopant and the lowest level unoccupied molecular orbital level (LUMO _Dopant ) of the dopant may be 0.5 eV or less.

In the organic light emitting diode device of the present invention, the delayed fluorescent compound is used as a host, and the organic light emitting layer may further include a dopant.

In the organic light emitting diode device of the present invention, the delayed fluorescent compound is used as a first dopant, the organic light emitting layer further includes a host and a second dopant, and the first triplet energy of the first dopant is that of the host. It may be less than the second triplet energy and greater than the third triplet energy of the second dopant.

In the organic light emitting diode device of the present invention, the organic light emitting layer includes a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer, and an electron injection layer, and the hole injection layer, the hole transport layer, and the above At least one of the light emitting material layer, the electron transport layer and the electron injection layer may include the delayed fluorescent compound.

In another aspect, the present invention provides a substrate, the above-described organic light emitting diode device disposed on the substrate, an encapsulation film covering the organic light emitting diode device, and a cover window on the encapsulation film. display device is provided.

Hereinafter, the structure and synthesis example of the delayed fluorescent compound according to an embodiment of the present invention, and an organic light emitting diode device using the same will be described.

The delayed fluorescent compound according to an embodiment of the present invention has a molecular formula in which an electron donor moiety, which is acridine, is bonded to an electron acceptor moiety through a linker or directly. , represented by Formula 1 below.

[Formula 1]

At this time, n is 0 or 1. That is, as in Formula 2-1 below, the electron-donor moiety of acridine has a structure in which the electron-donor moiety X is bonded through the linker Y, or as in Formula 2-2 below, acridine The electron donor moiety may have a structure directly bonded to the electron acceptor moiety X.

[Formula 2-1]

[Formula 2-2]

In Formulas 1, 2-1, and 2-2, the electron-accepting moiety X is a substituted or unsubstituted triazine, a substituted or unsubstituted dibenzothiophene, or a substituted or unsubstituted It is selected from diphenylsulfone, substituted or unsubstituted 4-azabenzimidazole, and substituted or unsubstituted benzimidazole. For example, the electron-accepting moiety X may be selected from materials represented by Formula 3 below.

[Formula 3]

In Formula 3, each of R1 to R4 may be independently substituted or unsubstituted aryl. For example, each of R1 to R4 may be unsubstituted phenyl.

In Chemical Formulas 1, 2-1, and 2-2, the linker Y is substituted or unsubstituted benzene. For example, linker Y may be selected from substances represented by Formula 4 below.

[Formula 4]

In Chemical Formula 4, each of R5 and R6 may independently be hydrogen or C1-C10 alkyl. For example, each of R5 and R6 can independently be hydrogen or methyl.

Such a delayed fluorescence compound includes both an electron donor moiety and an electron acceptor moiety, so that charge transfer within the molecule occurs easily and luminous efficiency is improved. In addition, a dipole is formed from the electron-donor moiety to the electron-acceptor moiety to increase the dipole moment inside the molecule, thereby further increasing the luminous efficiency.

In particular, since excitons in a triplet state are used for light emission in the delayed fluorescent compound of the present invention, the light emission efficiency of the delayed fluorescent compound is improved.

In addition, since acridine having a hexagonal structure is used as the electron donor moiety, steric hindrance with the electron acceptor moiety increases and the dihedral angle between the acridine electron donor moiety and the electron acceptor moiety increases. Therefore, since the formation of conjugation between the electron donor moiety and the electron acceptor moiety is restricted and the separation between the HOMO and the LUMO occurs smoothly, the improvement in luminous efficiency is further increased.

In addition, the electron donor moiety and the electron acceptor moiety are combined in the molecule, and the overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) is reduced. An electric field activation complex is formed, and the luminous efficiency of the delayed fluorescent compound is further improved.

As the distance between the electron-donor moiety and the electron-acceptor moiety increases by the linker, the overlap between the HOMO and the LUMO decreases, thereby reducing the difference between triplet energy and singlet energy (ΔE _ST ).

In addition, it is possible to minimize the red shift problem of light emitted from the light emitting layer including the delayed fluorescent compound due to the steric hindrance of the linker.

Referring to FIG. 1, which is a diagram for explaining a light emitting mechanism of a delayed fluorescent compound according to an embodiment of the present invention, in the delayed fluorescent compound of the present invention, both singlet excitons and triplet excitons participate in light emission to improve quantum efficiency. do.

That is, in the delayed fluorescent compound of the present invention, triplet excitons are activated by a field, and the triplet excitons and singlet excitons move to an intermediate state (I ₁ ) and ground state (S _{0 )} . ) and emits light. In other words, a transition occurs from the singlet state (S ₁ ) and triplet state (T ₁ ) to the intermediate state (I ₁ ) (S ₁ -> I ₁ <-T ₁ ), and both singlet and triplet excitons By participating in light emission, the light emission efficiency is improved. This is referred to as a filed activated delayed fluorescence (FADF) compound.

Conventional fluorescent materials cannot interconvert between a singlet state and a triplet state because HOMO and LUMO are spread throughout the molecule. (selection rule)

However, in the FADF compound as in the present invention, the interaction between HOMO and LUMO is small because the intramolecular HOMO and LUMO overlap is small. Therefore, a change in spin state of an electron does not affect other electrons, and a new charge transfer band that does not follow the selection rule is formed.

In addition, since the electron acceptor moiety and the electron donor moiety are spaced apart in the molecule, the dipole moment in the molecule exists in a polarized form. In a state where the dipole moment is polarized, the interaction between the HOMO and the LUMO becomes small, and the selection rule may not be followed. Therefore, in the FADF compound, a transition is possible from the triplet state (T ₁ ) and the singlet state (S ₁ ) to the intermediate state (I ₁ ), and triplet excitons participate in light emission.

When an organic light emitting diode device is driven, 25% of singlet state (S ₁ ) excitons and 75% of triplet state (T ₁ ) excitons undergo a systemic transition to an intermediate state (I ₁ ) by an electric field and ground state (S 1 ). ₀ ), the internal quantum efficiency theoretically becomes 100%.

For example, the delayed fluorescence compound of Formula 1 may be any one of the compounds of Formula 5 below.

[Formula 5]

The delayed fluorescent compound of the present invention includes acridine as an electron-donor moiety, and accordingly, the steric hindrance between the electron-donor moiety and the electron-acceptor moiety increases and the dihedral angle between the electron-donor and electron-acceptor moiety increases. It increases.

2a and 2b are views for explaining the molecular structure of a compound containing a carbazole electron-donating moiety, and FIGS. 3a and 3b are views for explaining the molecular structure of a compound containing an acridine electron-donating moiety. it is a drawing

Referring to FIGS. 2A and 2B , when carbazole is used as the electron donor moiety, the dihedral angle between the electron donor moiety and the electron acceptor moiety is about 44 degrees.

Meanwhile, referring to FIGS. 3A and 3B , when acridine is used as the electron donor moiety, the dihedral angle between the electron donor moiety and the electron acceptor moiety is about 89 degrees. That is, when acridine is included as the electron donor moiety, the dihedral angle between the electron donor moiety and the electron acceptor moiety increases, and the formation of conjugation between the electron donor moiety and the electron acceptor moiety is limited. Therefore, compared to a compound containing carbazole, separation between HOMO and LUMO occurs smoothly in a compound containing an acridine electron-donating moiety, and the improvement in luminous efficiency is further increased.

Hereinafter, synthetic examples of delayed fluorescent compounds according to embodiments of the present invention will be described.

-Synthesis example-

1. Synthesis of Compound 1

(1) Synthesis of compound a

[Scheme 1-1]

2,8-Dibromodibenzothiophene (14.6 mmol) and an acetic acid solvent were stirred in a nitrogen atmosphere. After adding hydrogen peroxide (64.8 mmol) and stirring at room temperature for about 30 minutes, the mixture was stirred under reflux for more than 12 hours. After completion of the reaction, 50 ml of distilled water was added, stirred, and washed. After filtering, the solid was washed a second time by stirring with an excess of hydrogen peroxide (retained for 30 minutes for 1 hour) and washed with distilled water. Filtered and dried to obtain compound a as a white solid. (Yield: 90%)

(2) Synthesis of compound b

[Scheme 1-2]

After mixing N-phenylanthraniliic acid (46.9 mmol) in a methanol solvent, the mixture was stirred in a nitrogen atmosphere. After further stirring for 10 minutes at 0 ° C, thionyl chloride (21.2 mmol) was slowly added dropwise. The mixed solution was stirred at 90°C for 12 hours or more. After completion of the reaction, the solvent was removed, and distilled water and ethyl acetate were added to perform extraction. Moisture was removed from the extracted organic layer using magnesium sulfate and the solvent was removed. A dark yellow liquid compound b was obtained by wet-refinement through column chromatography using hexane and ethyl acetate. (Yield: 81%)

(3) synthesis of compound c

[Scheme 1-3]

Compound b (38.1 mmol) was stirred in a tetrahydrofuran solvent in a nitrogen atmosphere. Methyl magnesium bromide (4.6 equivalents) was slowly added dropwise, and stirred at room temperature for 12 hours or more to react. After completion of the reaction, distilled water was added slowly and extracted using ethyl acetate. Water was removed from the organic layer extracted using magnesium sulfate and the solvent was removed. By wet purification through column chromatography using hexane and ethyl acetate, compound c in a yellow liquid state was obtained. (Yield: 87%)

(4) Synthesis of compound d

[Scheme 1-4]

Compound c (33.1 mmol) was added to an excess of phosphoric acid solvent (160 ml) and stirred at room temperature. After stirring for 16 hours or more, 200 to 250 ml of distilled water was slowly added. After stirring for 0.5 to 1 hour, the precipitated solid was filtered. The filtered solid was extracted using an aqueous sodium hydroxide solution and a dichloromethane solvent. Moisture was removed from the organic layer extracted using magnesium sulfate, and the organic solvent was removed to obtain compound d as a white solid. (Yield: 69%)

(5) synthesis of compound e

[Scheme 1-5]

Compound a was dissolved in a toluene solvent under a nitrogen atmosphere, and then phenylboronic acid (0.9 equivalent) was added. K ₂ CO ₃ (4 equivalents) was dissolved in distilled water and then added to the reaction mixture. A tetrahydrofuran solvent was added and palladium (Pd, 0.05 equivalent) was added. Thereafter, the reaction mixture was stirred while refluxing at 80 °C. After completion of the reaction, extraction was performed using an ethyl acetate solvent and distilled water, and moisture was removed from the extracted organic layer using magnesium sulfate. The remaining organic solvent was removed, and compound e in a solid state was obtained by wet purification using column chromatography using ethyl acetate and hexane. (Yield: 68%)

(6) Synthesis of Compound 1

[Scheme 1-6]

In a nitrogen atmosphere, compound e, compound d (1.1 equiv.), Pd(OAc) ₂ (0.019 equiv.), P(t-Bu) ₃ (50 wt%, 0.046 equiv.), and sodium tert-butoxide (1.9 equiv.) were dissolved in toluene. It was added to the solvent and stirred. The mixture was stirred under reflux for 12 hours at 120°C. After completion of the reaction, the mixture was cooled to room temperature and extracted with water and ethyl acetate. Water was removed from the extracted organic layer with magnesium sulfate, and the remaining organic solvent was removed. Compound 1 was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 55%)

2. Synthesis of Compound 2

(1) Synthesis of compound f

[Scheme 2-1]

In a nitrogen atmosphere, compound d (23.9 mmol), 1,4-dibromobenzene (35.8 mmol), palladium (II) acetate (2 mol%), tri-tert-butyl phosphate (5 mol%), sodium-tertiary- Butoxide (2.03 equivalents) was mixed with toluene solvent and stirred. The mixed solution was stirred under reflux and reacted for 12 hours. After completion of the reaction, extraction was performed using distilled water and ethyl acetate, and moisture was removed from the extracted organic layer using magnesium sulfate. After removing the remaining organic solvent, compound f was obtained by wet purification using column chromatography using ethyl acetate and hexane. (Yield: 81%)

(2) Synthesis of compound g

[Scheme 2-2]

In a nitrogen atmosphere, compound f, bis(pinacolate)diboron (1.2 eq.), [1,1-bis(diphenylphosphineo)ferrocene]palladium(II), dichloride dichloromethane, 1,1-bis(diphenylphosphino)ferrocene, potassium acetate were irradiated with light. was mixed in a 1,4-dioxane/toluene (1:1) solvent in a blocked flask and stirred. When all bubbles disappeared, the mixture was stirred at 120°C for 17 hours. After completion of the reaction, the mixture was cooled to room temperature, the solvent was removed, and the mixture was washed with toluene. Then, compound g was obtained by purification. (Yield: 90%)

(3) Synthesis of Compound 2

[Scheme 2-3]

After dissolving compound e in a toluene solvent in a nitrogen environment, compound g (1.2 equivalent) was added. Potassium carbonate (K ₂ CO ₃ , 8.8 equivalents) was dissolved in distilled water and then added to the reaction mixture. After further addition of tetrahydrofuran, palladium (Pd, 0.1 equivalent) was added. The reaction mixture was stirred at reflux at 80 °C. After completion of the reaction, extraction was performed using an aqueous sodium hydroxide solution and toluene, and moisture was removed from the extracted organic layer using magnesium sulfate. The remaining organic solvent was removed, and wet purification was performed by column chromatography using hexane. By recrystallization, compound 2 was obtained. (Yield: 56%)

3. Synthesis of Compound 3

(1) Synthesis of compound h

[Scheme 3-1]

4-phenylbromosulfone was dissolved in a toluene solvent under a nitrogen atmosphere, and then phenylboronic acid (0.9 equivalent) was added. K ₂ CO ₃ (4 equivalents) was dissolved in distilled water and then added to the reaction mixture. A tetrahydrofuran solvent was added and palladium (Pd, 0.05 equivalent) was added. Thereafter, the reaction mixture was stirred while refluxing at 80°C. After completion of the reaction, extraction was performed using an ethyl acetate solvent and distilled water, and moisture was removed from the extracted organic layer using magnesium sulfate. After removing the remaining organic solvent, compound h in a solid state was obtained by wet purification using column chromatography using ethyl acetate and hexane. (Yield: 75%)

(2) Synthesis of Compound 3

[Scheme 3-2]

In a nitrogen atmosphere, compound h, compound d (1.1 equiv.), Pd(OAc) ₂ (0.019 equiv.), P(t-Bu) ₃ (50 wt%, 0.046 equiv.), and sodium tert-butoxide (1.9 equiv.) were dissolved in toluene. It was added to the solvent and stirred. The mixture was stirred under reflux for 12 hours at 120°C. After completion of the reaction, the mixture was cooled to room temperature and extracted with water and ethyl acetate. Water was removed from the extracted organic layer with magnesium sulfate, and the remaining organic solvent was removed. Compound 3 was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 65%)

4. Synthesis of Compound 4

[Scheme 4]

After dissolving compound h in a toluene solvent in a nitrogen environment, compound g (1.2 equivalent) was added. Potassium carbonate (K ₂ CO ₃ , 8.8 equivalents) was dissolved in distilled water and then added to the reaction mixture. After further addition of tetrahydrofuran, palladium (Pd, 0.1 equivalent) was added. The reaction mixture was stirred at reflux at 80 °C. After completion of the reaction, extraction was performed using an aqueous sodium hydroxide solution and toluene, and moisture was removed from the extracted organic layer using magnesium sulfate. The remaining organic solvent was removed, and wet purification was performed by column chromatography using hexane. By recrystallization, compound 4 was obtained. (Yield: 60%)

5. Synthesis of Compound 5

[Scheme 5]

In a nitrogen atmosphere, catalysts Pd(dba) ₂ (5% mol) and P(t-Bu) ₃ (4% mol) were added to a toluene solvent and stirred for about 15 minutes. 2-chloro-4,6-diphenyl-1,3,5-triazine (33.8 mmol), compound d (33.8 mmol), and NaOt-Bu (60.6 mmol) were added and stirred at 90 ° C for 5 hours. After completion of the reaction, the mixture was filtered through celite and the remaining organic solvent was removed. The filtered solid was purified by column chromatography using hexane and dichloromethane, and wet purification was performed through recrystallization using hexane to obtain compound 5. (Yield: 59%)

6. Synthesis of Compound 6

[Scheme 6]

In a nitrogen atmosphere, 2-chloro-4,6-diphenyl-1,3,5-triazine, compound g (1.1 equiv.), Na ₂ CO ₃ (5 equiv.), NH ₄ Cl were dissolved in toluene/distilled water (1:1). It was added to the solvent and stirred. After stirring for 30 minutes while maintaining a nitrogen environment, tetrakis(triphenylphosphine)Pd(0) (0.05 equivalent) was added to the reaction mixture. Stirred for 10 minutes and stirred at 100° C. for 16 hours. After completion of the reaction, the mixture was cooled to room temperature and extracted with dichloromethane. After removing moisture from the extracted organic layer using magnesium sulfate, the remaining organic solvent was removed. After column chromatography purification using dichloromethane and hexane, solid compound 6 was obtained by recrystallization with chloroform. (Yield: 70%)

7. Synthesis of Compound 7

(1) Synthesis of compound i

[Scheme 7-1]

In a nitrogen environment, 4-azabenzimidazole, 1-bromo-4-iodobenzene (1.2 equiv.) and cesium carbonate (2 equiv. ) was added. The mixture was stirred under reflux for 16 hours at 110°C. After completion of the reaction, the DMF solvent was removed and extraction was performed with dichloromethane. After removing moisture from the extracted organic layer with magnesium sulfate, the remaining solvent was removed. Compound i was obtained by wet purification through column chromatography using ethyl acetate and hexane and recrystallization using dichloromethane. (Yield: 78%)

(2) Synthesis of Compound 7

[Scheme 7-2]

In a nitrogen atmosphere, compound i, compound d (1.1 equiv.), Pd(OAc) ₂ (0.019 equiv.), P(t-Bu) ₃ (50 wt%, 0.046 equiv.), and sodium tert-butoxide (1.9 equiv.) were mixed with toluene. It was added to the solvent and stirred. The mixture was stirred under reflux for 12 hours at 120°C. After completion of the reaction, the mixture was cooled to room temperature and extracted with water and ethyl acetate. Water was removed from the extracted organic layer with magnesium sulfate, and the remaining organic solvent was removed. Compound 7 was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 60%)

8. Synthesis of Compound 8

(1) Synthesis of compound j

[Scheme 8-1]

In a nitrogen environment, 4-azabenzimidazole, 1-bromo3,5-dimethyl-4-iodobenzene (1.3 equivalent) and cesium carbonate (2 equivalent) was added. The mixture was stirred under reflux for 16 hours at 110°C. After completion of the reaction, the DMF solvent was removed and extraction was performed with dichloromethane. After removing moisture from the extracted organic layer with magnesium sulfate, the remaining solvent was removed. Compound j was obtained by wet purification through column chromatography using ethyl acetate and hexane and recrystallization using dichloromethane. (Yield: 60%)

(2) Synthesis of Compound 8

[Scheme 8-2]

In a nitrogen atmosphere, compound j, compound d (1.1 equiv.), Pd(OAc) ₂ (0.019 equiv.), P(t-Bu) ₃ (50 wt%, 0.046 equiv.), and sodium tert-butoxide (1.9 equiv.) were mixed with toluene. It was added to the solvent and stirred. The mixture was stirred under reflux for 12 hours at 120°C. After completion of the reaction, the mixture was cooled to room temperature and extracted with water and ethyl acetate. Water was removed from the extracted organic layer with magnesium sulfate, and the remaining organic solvent was removed. Compound 8 was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 50%)

9. Synthesis of Compound 9

(1) Synthesis of compound k

[Scheme 9-1]

In a nitrogen environment, benzimidazole, 1-bromo-4-iodobenzene (1.2 equivalents) and cesium carbonate (2 equivalents) were added to the DMF solvent in which copper iodide (0.1 equivalents) and 1,10-phenanthroline (0.2 equivalents) were mixed. . The mixture was stirred under reflux for 16 hours at 110°C. After completion of the reaction, the DMF solvent was removed and extraction was performed with dichloromethane. After removing moisture from the extracted organic layer using magnesium sulfate, the remaining solvent was removed. Compound k was obtained by wet purification through column chromatography using ethyl acetate and hexane and recrystallization using dichloromethane. (Yield: 80%)

(2) Synthesis of Compound 9

[Scheme 9-2]

In a nitrogen atmosphere, compound k, compound d (1.1 equiv), Pd(OAc) ₂ (0.019 equiv) and P(t-Bu) ₃ (50 wt%, 0.046 equiv), NaOt-Bu (sodium tert-butoxide, 1.9 equivalent) into a toluene solvent and stirred. The mixture was stirred under reflux for 12 hours at 120°C. After completion of the reaction, the mixture was allowed to stand at room temperature and extracted with water and ethyl acetate. Moisture was removed from the extracted organic layer with magnesium sulfate, and the remaining organic solvent was removed. Compound 9 was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 62%)

10. Synthesis of Compound 10

(1) Synthesis of Compound 1

[Scheme 10-1]

In a nitrogen environment, benzimidazole, 1-bromo3,5-dimethyl-4-iodobenzene (1.3 equiv) and cesium carbonate (2 equiv) were mixed in a DMF solvent containing copper iodide (0.1 equiv) and 1,10-phenanthroline (0.2 equiv). was added. The mixture was stirred under reflux for 16 hours at 110°C. After completion of the reaction, the DMF solvent was removed and extraction was performed with dichloromethane. After removing moisture from the extracted organic layer with magnesium sulfate, the remaining solvent was removed. Compound 1 was obtained by wet purification through column chromatography using ethyl acetate and hexane and recrystallization using dichloromethane. (Yield: 58%)

(2) Synthesis of Compound 10

[Scheme 10-2]

In a nitrogen atmosphere, compound 1, compound d (1.1 equiv), Pd(OAc) ₂ (0.019 equiv) and P(t-Bu) ₃ (50 wt%, 0.046 equiv), NaOt-Bu (sodium tert-butoxide, 1.9 equivalent) into a toluene solvent and stirred. The mixture was stirred under reflux for 12 hours at 120°C. After completion of the reaction, the mixture was allowed to stand at room temperature and extracted with water and ethyl acetate. After removing moisture from the extracted organic layer with magnesium sulfate, the remaining organic solvent was removed. Compound 10 was obtained by wet purification through column chromatography using hexane and ethyl acetate. (Yield: 46%)

The mass spectrometry results of compounds 1 to 10 are shown in Table 1.

The emission characteristics of the compounds 3, 6, 7, and 9 (Com3, Com6, Com7, and Com9) were measured under O ₂ -free conditions using Quantarus tau equipment from Hamamatsu, and the measurement results are shown in Table 2 and FIGS. 4A to 4D. described.

As shown in Table 2 and FIGS. 4A to 4D, each of Compounds 3, 6, 7, and 9 (Com3, Com6, Com7, and Com9), which are delayed fluorescent compounds according to the present invention, has several hundred to tens of thousands of nano-seconds (ns). showed delayed fluorescence.

As described above, the delayed fluorescent compound of the present invention is field activated, so that the singlet state (S ₁ ) excitons and the triplet state (T ₁ ) excitons are transitioned to an intermediate state (I ₁ ), and both of them emit light. take part in

Such a field-activated complex is a monomolecular compound having both an electron-donor moiety and an electron-acceptor moiety in one molecule, and electrons easily move within the molecule. In the field-activated complex, electrons may move from the electron-donor moiety to the electron-acceptor moiety under specific conditions, causing charge separation to occur within the molecule.

The field activation complex is formed by the external environment, which can be easily confirmed by comparing the absorption wavelength and emission wavelength of the solution state using various solvents.

In the above equation, Δν is the stock shift value, and νabs and νfl are the wavenumbers of the maximum absorption wavelength and maximum emission wavelength, respectively. Also, h is Plank's constant, c is the velocity of light, a is the onsager cavity radius, and Δμ is the difference between the dipole moment of the excited state and the dipole moment of the ground state (Δμ = μ _e -μ _g ).

Δf is a value representing the orientational polarizability of the solvent and is expressed by the dielectric constant (ε) and the refractive index (n) of the solvent as shown in the following formula.

Formation of the field-activated complex can be confirmed by comparing absorption wavelengths and emission wavelengths in a solution state using various solvents. This is because the degree of polarization (magnitude of the dipole moment) at the time of excitation is determined by the polarity of the surroundings.

The directional polarization of the mixed solvent, Δf, can be used by calculating the directional polarization values of the pure solvent as a ratio of the mole fraction, and the formation of the field activated complex can be determined by using the above equation (Lippert-Mataga equation) to determine Δf and Δν It can be judged by checking whether a linear relationship appears when plotting .

That is, the field activation complex is stabilized according to the directional polarization of the solvent, and the emission wavelength shifts to a longer wavelength according to the stabilization degree. Accordingly, when the field-activated complex is formed, Δf and Δν form a linear graph, and conversely, when Δf and Δν form a linear graph, it can be seen that the light emitting material is a field-activated complex.

In the delayed fluorescence compound of the present invention, 25% of the singlet state excitons and 75% of the triplet state excitons are in the middle of the singlet state and the triplet state by the external environment, for example, the electromagnetic field generated when the organic light emitting diode device is driven. This is interpreted as causing intersystem crossing, and quantum efficiency is improved because light emission occurs while going from this intermediate state to the ground state. That is, luminous efficiency is improved by not only singlet state excitons but also triplet state excitons participating in light emission in the fluorescent material.

Hereinafter, the performance of the organic light emitting diode using the delayed fluorescent compound of the present invention and the organic light emitting diode using the comparative material of Formula 6 will be compared and described.

device fabrication

After the ITO substrate was patterned so that the light emitting area had a size of 3 mm X 3 mm, it was cleaned. Next, the substrate was transferred into a vacuum deposition chamber. After setting the base pressure to about 10 ^-6 ~ 10 ^-7 Torr, on the anode, ITO, i) hole injection layer (500Å, NPB (N,N'-di(naphthalen-1-yl)-N,N'- diphenyl-benzidine)), ii) hole transport layer (100Å, mCP (N,N'-Dicarbazolyl-3,5-benzene)), iii) light-emitting material layer (350Å, host (bis{2-[di(phenyl)phosphino ]phenyl}ether oxide/dopant (6%)), iv) electron transport layer (300Å, 1,3,5-tri(phenyl-2-benzimidazole)-benzene), v) electron injection layer (LiF), vi) cathode (Al) was sequentially laminated.

(1) Comparative Example (Ref)

In the above-described device, the compound of Formula 6 was used as a dopant of the light emitting material layer.

(2) Experimental Example 1 (Ex1)

In the above device, compound 3 was used as a dopant for the light emitting material layer.

(3) Experimental Example 2 (Ex2)

In the above device, compound 6 was used as a dopant for the light emitting material layer.

(4) Experimental Example 3 (Ex3)

In the above device, compound 7 was used as a dopant for the light emitting material layer.

(5) Experimental Example 4 (Ex4)

In the above device, compound 9 was used as a dopant for the light emitting material layer.

[Formula 6]

As can be seen from Table 3, the organic light emitting diode device using the delayed fluorescent compound of the present invention has improved characteristics in terms of driving voltage and luminous efficiency.

An embodiment of an organic light emitting diode device including the delayed fluorescent compound is shown in FIG. 5 .

As shown in FIG. 5, the organic light emitting diode device includes a light emitting diode (E) positioned on a substrate (not shown).

The light emitting diode (E) includes a first electrode 110 serving as an anode, a second electrode 130 serving as a cathode, and an organic light emitting layer 120 formed between the first and second electrodes 110 and 130. made up of

Meanwhile, although not shown, a display device may be formed by including an encapsulation film including an inorganic layer and an organic layer and covering the light emitting diode E, and a cover window on the encapsulation film. In this case, since the substrate and the cover window have flexible characteristics, a flexible display device may be formed.

The first electrode 110 is made of a material having a relatively high work function value, for example, indium-tin-oxide (ITO), and the second electrode 130 is made of a material having a relatively low work function value, for example, indium-tin-oxide (ITO). For example, it is made of aluminum (Al) or aluminum alloy (AlNd). In addition, the organic light emitting layer 120 is composed of red, green, and blue organic light emitting patterns.

The organic light emitting layer 120 may have a single-layer structure, or may have a multi-layer structure to improve light emitting efficiency. For example, a hole injection layer (HIL) 121, a hole transporting layer (HTL) 122, and an emitting material layer (EML) are sequentially formed from the first electrode 110. 123, an electron transporting layer (ETL) 124, and an electron injection layer (EIL) 125.

Here, at least one of the hole injection layer 121, the hole transport layer 122, the light emitting material layer 123, the electron transport layer 124, and the electron injection layer 125 includes the delayed fluorescent compound represented by Chemical Formula 1. It can be done by

For example, the light emitting material layer 123 may include the delayed fluorescent compound represented by Formula 1 above. The light emitting material layer 123 includes the delayed fluorescent compound of the present invention as a dopant material, may be doped with a host of about 1 to 30 wt%, and emits blue light.

The difference between the highest level occupied molecular orbital level of the host (HOMO _Host ) and the highest level occupied molecular orbital level of the dopant (HOMO _Dopant ) (|HOMO _Host -HOMO _Dopant |) or the lowest level unoccupied molecular orbital level of the host (LUMO _Host ) and the lowest unoccupied molecular orbital level (LUMO _Dopant ) of the dopant (|LUMO _Host -LUMO _Dopant |) is set to be 0.5 eV or less. Accordingly, charge transfer efficiency from the host to the dopant is improved.

For example, as a host that satisfies these conditions, any one of Formula 7 below may be used. (Bis[2-(diphenylphosphino)phenyl]ether oxide (DPEPO), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT), 2,8-di(9H-carbazol-9-yl)dibenzothiophene (DCzDBT), m respectively -bis(carbazol-9-yl)biphenyl (m-CBP), diphenyl-4-triphenylsilylphenyl-phosphine oxide (TPSO1), 9-(9-phenyl-9H-carbazol-6-yl)-9H-carbazole (CCP) )

[Formula 7]

At this time, the triplet energy of the dopant is smaller than the triplet energy of the host, and the difference between the singlet energy of the dopant and the triplet energy of the dopant (ΔE _ST ) is characterized in that 0.3 eV or less. The smaller ΔE _ST , the higher the luminous efficiency, and in the delayed fluorescent compound of the present invention, even if the difference between the singlet energy and triplet energy (ΔE _ST ) of the dopant is relatively large, about 0.3 eV, the singlet state (S ₁ ) Excitons and triplet states (T ₁ ) Excitons can transition to intermediate states (I ₁ ). (ΔE _ST ≤0.3)

On the other hand, the light emitting material layer 123 may include a delayed fluorescent compound of the present invention as a host material, and may include a dopant doped at about 1 to 30 wt% with respect to the host material, and emits blue light. Since development of a blue host with excellent characteristics is not sufficient, the degree of freedom in host selection can be increased by using the delayed fluorescent compound of the present invention as a host material.

At this time, the triplet energy of the dopant is smaller than the triplet energy of the host, which is the delayed fluorescent compound of the present invention.

In addition, the light emitting material layer 123 includes the delayed fluorescent compound of the present invention as a first dopant material and further includes a host material and a second dopant material, and the sum of the doped first and second dopant materials is It is doped at about 1 to 30 wt% with respect to the host material, thereby emitting blue light. Since the light emitting material layer 123 includes a host material and first and second dopant materials, light emitting efficiency and color are further improved.

At this time, the triplet energy of the first dopant, which is the delayed fluorescent compound of the present invention, is smaller than the triplet energy of the host and greater than the triplet energy of the second dopant. Also, at this time, the difference between the singlet energy of the first dopant and the triplet energy of the first dopant (ΔE _ST ) is 0.3 eV or less. The smaller ΔE _ST is, the higher the luminous efficiency is, and even if the difference between singlet energy and triplet energy (ΔE _ST ) of the first dopant, which is the delayed fluorescence compound of the present invention, is relatively large, about 0.3 eV, the singlet state ( S ₁ ) excitons and triplet state (T ₁ ) excitons may transition to an intermediate state (I ₁ ). (ΔE _ST ≤0.3)

As described above, the delayed fluorescent compound of the present invention contains both an electron donor moiety and an electron acceptor moiety, and the electron donor moiety has a large steric hindrance with the electron acceptor moiety. Since it is credin, the luminous efficiency is further improved. In addition, a dipole is formed from the electron-donor moiety to the electron-acceptor moiety to increase the dipole moment inside the molecule, thereby further increasing the luminous efficiency. In addition, since excitons in the triplet state are used for light emission in the delayed fluorescent compound of the present invention, the light emission efficiency is improved.

As the distance between the electron-donor moiety and the electron-acceptor moiety increases by the linker, the overlap between the HOMO and the LUMO decreases, thereby reducing the difference between triplet energy and singlet energy (ΔE _ST ).

In addition, it is possible to minimize the red shift problem of light emitted from the light emitting layer including the delayed fluorescent compound due to the steric hindrance of the linker.

Therefore, the organic light emitting diode device including the delayed fluorescent compound of the present invention has improved light emitting efficiency and can implement high quality images.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention within the scope not departing from the technical spirit and scope of the present invention described in the claims below. You will understand that it can be done.

110: first electrode 120: organic light emitting layer
121: hole injection layer 122: hole transport layer
123: light emitting material layer 124: electron transport layer
125: electron injection layer 130: second electrode
E: organic light emitting diode

Claims (17)

delete A delayed fluorescent compound selected from compounds represented by Formula 4 below, or represented by Formula 1 below, X is selected from Formula 2, and Y is selected from Formula 3 below. (n is 0 or 1)
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

(R5 and R6 are each independently selected from hydrogen or C1-C10 alkyl.)
According to claim 2,
The delayed fluorescent compound is any one of the following compounds.

According to claim 2,
A difference between singlet energy and triplet energy of the delayed fluorescent compound is 0.3 eV or less.

delete a first electrode;
a second electrode facing the first electrode;
An organic light emitting layer positioned between the first and second electrodes;
The organic light emitting layer,
An organic light emitting diode device comprising a delayed fluorescent compound selected from compounds of Formula 4 below, or represented by Formula 1 below, X is selected from Formula 2, and Y is selected from Formula 3 below. (n is 0 or 1)
[Formula 1]

[Formula 2]

[Formula 3]

[Formula 4]

(In Formula 3, each of R5 and R6 is independently selected from hydrogen or C1-C10 alkyl.)
According to claim 6,
The delayed fluorescent compound is any one of the following compounds organic light emitting diode device.

According to claim 6,
The difference between singlet energy and triplet energy of the delayed fluorescent compound is 0.3 eV or less organic light emitting diode device.
According to claim 6,
The delayed fluorescent compound is used as a dopant, and the organic light emitting layer further comprises a host.
According to claim 9,
The difference between the highest level occupied molecular orbital level of the host (HOMO _Host ) and the highest level occupied molecular orbital level of the dopant (HOMO _Dopant ) (|HOMO _Host -HOMO _Dopant |) or the lowest level unoccupied molecular orbital level of the host (LUMO _Host ) and the lowest unoccupied molecular orbital level (LUMO _Dopant ) of the dopant (|LUMO _Host -LUMO _Dopant |) is less than 0.5 eV organic light emitting diode device.
According to claim 6,
The delayed fluorescent compound is used as a host, and the organic light emitting layer further comprises a dopant.
According to claim 6,
The delayed fluorescent compound is used as a first dopant, and the organic light emitting layer further includes a host and a second dopant,
A first triplet energy of the first dopant is less than a second triplet energy of the host and greater than a third triplet energy of the second dopant.
According to claim 6,
The organic light emitting layer includes a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer and an electron injection layer,
At least one of the hole injection layer, the hole transport layer, the light emitting material layer, the electron transport layer, and the electron injection layer includes the delayed fluorescence compound.
a substrate;
an organic light emitting diode device according to one of claims 6 to 13 positioned on the substrate;
an encapsulation film covering the organic light emitting diode device;
A display device including a cover window on the encapsulation film.
A delayed fluorescent compound represented by Formula 1 below, X is selected from Formula 2, and Y is selected from Formula 3 below.
[Formula 1]

[Formula 2]

[Formula 3]

(In Formula 2, each of R1 and R2 is independently selected from substituted or unsubstituted aryl, and in Formula 3, each of R5 and R6 is independently selected from hydrogen or C1-C10 alkyl.)
According to claim 15,
The delayed fluorescent compound is any one of the following compounds.

a first electrode;
a second electrode facing the first electrode;
An organic light emitting layer positioned between the first and second electrodes;
The organic light emitting layer is an organic light emitting diode device comprising the delayed fluorescence compound of claim 15 or claim 16.

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